feat: add meta hints user marks for metadata heuristic override

Users can now right-click nodes and assign meta hints
(primary_model, primary_sampler, positive_prompt,
negative_prompt) to override the metadata processor's
heuristic inference.

- Store extra_data from the API request so workflow node
  properties (including lm_marker_role) are accessible
  during metadata processing.
- _get_user_marks scans extra_data.extra_pnginfo.workflow
  for meta_* marks, falling back to prompt.original_prompt.
- extract_generation_params checks user marks before
  heuristic inference for sampler, model, and prompts.
- Warn on duplicate marks or invalid marked nodes.

py/metadata_collector/metadata_hook.py

@@ -135,10 +135,13 @@ class MetadataHook:
                 # Store the dynprompt reference for node lookups
                 if hasattr(prompt, 'original_prompt'):
                     registry.set_current_prompt(prompt)
-            
+
+                # Store extra_data for accessing full workflow node properties
+                registry.set_extra_data(extra_data)
+
             # Execute the original function
             return original_execute(*args, **kwargs)
-            
+
         # Replace the functions
         execution._map_node_over_list = map_node_over_list_with_metadata
         execution.execute = execute_with_prompt_tracking
@@ -202,6 +205,9 @@ class MetadataHook:
                 if hasattr(prompt, 'original_prompt'):
                     registry.set_current_prompt(prompt)
 
+                # Store extra_data for accessing full workflow node properties
+                registry.set_extra_data(extra_data)
+
             # Execute the original function
             return await original_execute(*args, **kwargs)